U.S. patent application number 12/189468 was filed with the patent office on 2010-02-11 for apparatus and method for cultivating algae.
Invention is credited to Gary Erb, David Ross Peterson.
Application Number | 20100034050 12/189468 |
Document ID | / |
Family ID | 41652835 |
Filed Date | 2010-02-11 |
United States Patent
Application |
20100034050 |
Kind Code |
A1 |
Erb; Gary ; et al. |
February 11, 2010 |
Apparatus and Method for Cultivating Algae
Abstract
Apparatus and methods for cultivating photosynthetic organisms,
such as algae, in a bioreactor may include a bioreactor having a
primary tank. Light and carbon dioxide are provided in the tank
sufficient to promote algae growth. The algae is agitated inside
the tank to increase the amount of algae receiving sufficient light
exposure inside the tank. Agitation may be provided by a closed
loop circulation system or a mixer having a plurality of rotating
blades. The gas source may be positioned and oriented with respect
to the light source to keep the light source free of adhered
material.
Inventors: |
Erb; Gary; (Crystal Lake,
IL) ; Peterson; David Ross; (Dixon, IL) |
Correspondence
Address: |
MILLER, MATTHIAS & HULL
ONE NORTH FRANKLIN STREET, SUITE 2350
CHICAGO
IL
60606
US
|
Family ID: |
41652835 |
Appl. No.: |
12/189468 |
Filed: |
August 11, 2008 |
Current U.S.
Class: |
366/342 ;
435/292.1 |
Current CPC
Class: |
C12M 27/02 20130101;
B01F 5/10 20130101; C12M 29/06 20130101; C12M 31/10 20130101; B01F
5/104 20130101; C12M 21/02 20130101; B01F 3/04248 20130101; B01F
7/22 20130101; B01F 3/04985 20130101; B01F 7/00633 20130101; B01F
7/00058 20130101; C12M 27/20 20130101; B01F 3/04531 20130101; B01F
2003/04893 20130101 |
Class at
Publication: |
366/342 ;
435/292.1 |
International
Class: |
B01F 3/00 20060101
B01F003/00; C12M 1/06 20060101 C12M001/06 |
Claims
1. A bioreactor for cultivating photosynthetic organisms,
comprising: a primary tank including a sidewall oriented along a
longitudinal axis; a mixer disposed inside the tank; a light source
disposed inside the tank; and a sparger disposed inside the tank
and adapted to fluidly communicate with a source of carbon
dioxide.
2. The bioreactor of claim 1, in which the primary tank sidewall is
cylindrical.
3. The bioreactor of claim 2, in which the light source comprises
at least one curved panel coupled to an interior surface of the
sidewall.
4. The bioreactor of claim 1, in which the mixer comprises a shaft
and a plurality of rotating blades coupled to the shaft.
5. The bioreactor of claim 4, in which the plurality of rotating
blades are coupled to the shaft at specific elevations to create
discrete sets of rotating blades.
6. The bioreactor of claim 5, in which each rotating blade
comprises at least first and second sections, and in which each
rotating blade first section is configured to generate fluid flow
in a first axial direction and each rotating blade second section
is configured to generate fluid flow in a second, opposite axial
direction.
7. The bioreactor of claim 6, in which each rotating blade further
comprises a third section, and in which each rotating blade third
section is configured to generate fluid flow in one of the first
and second axial directions.
8. The bioreactor of claim 5, in which the mixer further comprises
a plurality of non-rotating blades coupled to an interior surface
of the primary tank sidewall at specific elevations to create
discrete sets of non-rotating blades.
9. The bioreactor of claim 8, in which the sets of rotating blades
and non-rotating blades alternate along the longitudinal axis.
10. The bioreactor of claim 8, in which each non-rotating blade
comprises at least first and second sections, and in which each
non-rotating blade first section is configured to generate fluid
flow in a first axial direction.
11. The bioreactor of claim 8, in which the light source comprises
a plurality of individual lights disposed on at least some of the
non-rotating blades.
12. The bioreactor of claim 1, in which the gas source comprises a
plurality of gas nozzles disposed inside the tank.
13. The bioreactor of claim 12, in which at least some of the
nozzles are positioned to direct a gas jet toward the light
source.
14. The bioreactor of claim 1, in which the light source comprises
a plurality of individual lights disposed inside the primary
tank.
15. A bioreactor for cultivating photosynthetic organisms disposed
in a fluid, comprising: a primary tank including a sidewall
oriented along a longitudinal axis and defining an inlet end and an
outlet end; an inlet pipe coupled to the primary tank inlet end; an
inlet valve disposed in the inlet pipe and movable between open and
closed positions; an outlet pipe coupled to the primary tank outlet
end; an outlet valve disposed in the outlet pipe and movable
between open and closed positions; a recirculation pipe having a
first end coupled to the primary tank inlet end and a second end
coupled to the primary tank outlet end; a recirculation pump
disposed in the recirculation pipe; a light source disposed in at
least one of the recirculation pipe and the primary tank; and a gas
source disposed inside the tank.
16. The bioreactor of claim 15, in which the bioreactor has an
agitation mode in which the inlet and outlet valves are placed in
the closed position and the recirculation pump is operated to
agitate the fluid.
17. The bioreactor of claim 15, in which the longitudinal axis is
substantially horizontal.
18. The bioreactor of claim 17, in which the primary tank is at
least partially disposed underground.
19. A method for agitating photosynthetic organisms in a fluid
disposed within a bioreactor, comprising: providing a primary tank
including a sidewall oriented along a longitudinal axis; providing
a mixer disposed inside the tank; providing a light source inside
the tank; providing a gas source inside the tank; operating the
mixer to create a complex fluid flow pattern inside the primary
tank, in which the complex fluid flow pattern includes at least a
first and second fluid path sections, wherein the first fluid path
section flows substantially in a first direction along the
longitudinal axis and the second fluid path section flows
substantially in a second, opposite direction along the
longitudinal axis.
20. The method of claim 19, in which the complex fluid flow pattern
further has a third fluid path section flowing substantially in
either the first or second direction along the longitudinal axis.
Description
FIELD OF THE DISCLOSURE
[0001] This disclosure generally relates to an apparatus and method
for growing photosynthetic microorganisms, and more particularly
for growing algae. Certain embodiments also relate to a system for
producing useful products from algae, such as biofuels and
protein.
BACKGROUND OF THE DISCLOSURE
[0002] A variety of methods and technologies exist for cultivating
and harvesting biomass such as, for example, mammalian, animal,
plant, and insect cells, as well as various species of bacteria,
algae, plankton, and protozoa. These methods and technologies may
include open-air systems and closed systems. Algal biomasses, for
example, are often cultured in open-air systems (e.g. ponds, lakes,
raceway ponds, and the like) that are subject to contamination.
These open-air systems are further limited by an inability to
substantially control the various process parameters (e.g.,
temperature, incident light intensity, flow, pressure, nutrients,
and the like) involved in cultivating algae.
[0003] Alternatively, algae may be cultivated in closed systems
called bioreactors. Closed systems allow for better control of the
process parameters but are typically more costly to set up and
operate. In addition, conventional closed systems are limited in
their ability to provide sufficient light to sustain dense
populations of photosynthetic organisms cultivated within.
[0004] Biomasses have many beneficial and commercial uses
including, for example, as pollution control agents, fertilizers,
food supplements, cosmetic additives, pigment additives, and energy
sources just to name a few. For example, algal biomasses are used
in wastewater treatment facilities to capture fertilizers. Algal
biomasses are also used to make biofuels.
[0005] Bioreactors used for growing photosynthetic organisms
typically employ a constant intensity light source. A key factor
for cultivating biomasses such as algae in bioreactors is provided
in controlling the light necessary for the photosynthetic process.
If the light intensity is too high or the exposure time to long,
growth of the algae is inhibited. Moreover, as the density of the
algae cells in the bioreactors increases, algae cells closer to the
light source limit the ability of those algae cells that are
further away from absorbing light. This factor has limited the size
of conventional, closed bioreactors.
[0006] Commercial acceptance of bioreactors is dependent on a
variety of factors such as cost to manufacture, cost to operate,
reliability, durability, and scalability. Commercial acceptance of
bioreactors is also dependent on their ability to increase biomass
production, while decreasing biomass production costs. Accordingly,
it may be desirable to provide a bioreactor capable of operating at
a commercial scale.
SUMMARY OF THE DISCLOSURE
[0007] A bioreactor for cultivating photosynthetic organisms
includes a primary tank having a sidewall oriented along a
longitudinal axis, a mixer disposed inside the tank, a light source
disposed inside the tank, and a sparger disposed inside the tank
and adapted to fluidly communicate with a source of carbon
dioxide.
[0008] According to additional aspects, a bioreactor is provided
for cultivating photosynthetic organisms disposed in a fluid. The
bioreactor includes a primary tank having a sidewall oriented along
a longitudinal axis and defining an inlet end and an outlet end. An
inlet pipe is coupled to the primary tank inlet end and an inlet
valve is disposed in the inlet pipe and movable between open and
closed positions. An outlet pipe is coupled to the primary tank
outlet end and an outlet valve is disposed in the outlet pipe and
movable between open and closed positions. A recirculation pipe has
a first end coupled to the primary tank inlet end and a second end
coupled to the primary tank outlet end, and a recirculation pump is
disposed in the recirculation pipe. A light source is disposed in
at least one of the primary tank and recirculation pipe, and a gas
source disposed inside the tank.
[0009] According to further aspects, a method for agitating
photosynthetic organisms in a fluid disposed within a bioreactor
includes providing a primary tank including a sidewall oriented
along a longitudinal axis, a mixer disposed inside the tank, a
light source inside the tank, and a gas source inside the tank. The
method includes operating the mixer to create a complex fluid flow
pattern inside the primary tank, in which the complex fluid flow
pattern includes at least a first and second fluid path sections,
wherein the first fluid path section flows substantially in a first
direction along the longitudinal axis and the second fluid path
section flows substantially in a second, opposite direction along
the longitudinal axis.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] For a more complete understanding of the disclosed methods
and apparatus, reference should be made to the embodiments
illustrated in greater detail on the accompanying drawings,
wherein;
[0011] FIG. 1 is a schematic illustration of a bioreactor according
to the present disclosure having a horizontally aligned primary
tank;
[0012] FIG. 2 is a schematic illustration of an alternative
embodiment of a bioreactor having a vertically oriented primary
tank;
[0013] FIG. 3 is a schematic illustration of an algae cultivation
and reproduction system including the bioreactor of FIG. 2;
[0014] FIGS. 4A and 4B are schematic plan views illustrating
alternative impeller in the bioreactor of FIG. 2;
[0015] FIG. 5 is an enlarged plan view of a portion of an impeller
usable in the bioreactor of FIG. 2;
[0016] FIGS. 6A and 6B are side elevation views, in cross-section,
of the impeller of FIG. 5 taken along lines 6a-6a and 6b-6b
respectively;
[0017] FIGS. 7A and 7B are schematic perspective views of
alternative turbine blades usable in the bioreactor of FIG. 2;
[0018] FIGS. 8A and 8B are schematic perspective views of a further
impeller embodiment having primary and outer sections that are
adjustable with respect to each other;
[0019] FIGS. 9A and 9B are perspective schematic illustrations of a
yet another impeller embodiment having inner, primary, and outer
sections that are adjustable with respect to one another;
[0020] FIGS. 10A-10D are schematic illustrations showing possible
fluid flow paths inside the primary tank;
[0021] FIGS. 11A and 11B are schematic illustrations showing
fluid-filled tubing surrounding a horizontally orientated primary
tank, respectively;
[0022] FIG. 12A is a schematic side elevation view, in
cross-section, of a bioreactor employing a set of rotating blades
and a set of non-rotating blades;
[0023] FIG. 12B is a schematic plan view of the bioreactor of FIG.
12A;
[0024] FIG. 13 is an enlarged schematic perspective view of a
single rotating blade and a single non-rotating blade from FIG.
12;
[0025] FIG. 14 is an enlarged schematic perspective view of an
alternative embodiment of rotating and non-rotating blades;
[0026] FIG. 15 is an enlarged schematic perspective view of an
alternative embodiment of rotating and non-rotating blades;
[0027] FIG. 16 is an enlarged schematic perspective view of an
alternative embodiment of rotating and non-rotating blades; and
[0028] FIG. 17 is a schematic perspective view of a bioreactor
employing curved light panels.
[0029] It should be understood that the drawings are not
necessarily to scale and the disclosed embodiments are sometimes
illustrated diagrammatically in partial views. In certain
instances, details which are not necessary for an understanding of
the disclosed methods and apparatus, or which render other details
difficult to perceive, may have been omitted. It should be
understood, of course, that this disclosure is not limited to the
particular embodiments illustrated herein.
DETAILED DESCRIPTION OF THE DISCLOSURE
[0030] A method and apparatus for cultivating algae is disclosed
that uses waste and products from other systems as inputs. The
algae produced by the method and apparatus contain polysaccharide,
proteins, and lipids, which may be further processed into
biodiesel, glycerin and mono sugars (which may be further fermented
into ethanol and other alcohol products). The exemplary embodiments
employ a closed bioreactor system to produce the algae. The system
generally includes a primary tank for receiving a slurry of water
and algae. The tank further includes a light source, means for
mixing the fluid, a carbon dioxide, and a heat source. The light,
fluid mixing, carbon dioxide, are controlled to produce an
environment inside the tank that is conducive to producing and
cultivating algae. The bioreactor increases algae yield by using a
plurality of lights and/or agitating the fluid inside the tank.
[0031] A first embodiment of a bioreactor is illustrated in FIG. 1.
The bioreactor 20 generally includes a primary tank 22 disposed
along a horizontal axis 24. The tank 22 may have any commercially
feasible size. For example, when the tank 22 is cylindrical, it may
have a diameter greater than one foot, and preferably five to eight
feet or more, if sufficient space and soil depth are available. The
length of the tank is also largely dependent on the available space
and volume of algae cultivation desired. For example, the tank 22
may be twelve to twenty-two feet long or more. Similarly, the
volume of the tank may be selected according to desired production
rate and available space, such as approximately 1,500-5,000
gallons.
[0032] The primary tank 22 is preferably insulated, such as by
surrounding the tank 22 with temperature controlled, fluid-filled
tubing 23 as best shown in FIG. 11B. Additionally or alternatively,
the primary tank 22 may be located partially or fully underground
to provide natural insulation.
[0033] The primary tank 22 defines a first or inlet end 26 or a
second or outlet end 28. An inlet pipe 30 is coupled to the first
end 26 while an outlet pipe 32 is coupled to the outlet end 28.
Inlet and outlet valves, 31, 33, are disposed in the inlet and
outlet pipes 30, 32, respectively, to control fluid flow into and
out of the primary tank 22. The primary tank 22 may further include
an access hatch 34 and associated lid 36. The axis hatch 34 is
sized to permit axis to the interior of the primary tank 22 for
inspection and maintenance purposes. The lid 36 preferably forms an
airtight seal when closed to help maintain the desired process
parameters inside the tank 22 and to prevent gas from escaping from
the tank.
[0034] The exemplary bioreactor 20 further includes a circulation
system 40 that mixes and agitates the fluid inside the primary tank
22. In the illustrated embodiment, the circulation system 40
includes a circulation pipe 42 having a circulation pump 44
disposed therein. The circulation pipe 42 may have a first end 46
fluidly communicating with the inlet end of the primary tank 22 and
a second end 48 fluidly communicating with the outlet end of the
tank 22. The pump 44 may be orientated so that fluid flows through
the circulation pipe from the first end 46 to the second end 48. It
will be appreciated that this fluid flow agitates and mixes the
fluid inside the tank thereby to expose different portions of the
fluid through the interior tank surface.
[0035] The bioreactor 20 further includes a sparger 50 for
introducing carbon dioxide into the primary tank 22. In the
illustrated embodiment, a plurality of nozzles 52 are formed around
a periphery of the tank 22 and are orientated to discharge into the
tank interior. The nozzles 52 fluidly communicate with a carbon
dioxide source (not shown). In operation, the nozzles 52 inject
carbon dioxide gas into the interior, which is subsequently
consumed during the photosynthesis process. The sparger 50 may also
assist with agitating the algae slurry.
[0036] Carbon dioxide may be introduced into the primary tank 22
via other alternatives, should bubble lysis of the algae cells
become a problem. Bubble lysis is the lysis of algae cells as
bubbles of carbon dioxide burst. While a certain level of bubble
lysis is inevitable inside the primary tank 22, a significant level
of bubble lysis is detrimental to algae cultivation inside the tank
22. Should bubble lysis become an issue, the carbon dioxide may be
injected into the algae slurry prior to introduction into the
primary tank 22, thereby mitigating the amount of bubble lysis
inside the tank.
[0037] The bioreactor 20 may also include a light apparatus 60 for
providing light inside the primary tank 22. In the illustrated
embodiment, the light apparatus 60 includes a plurality of
individual lights 62 positioned along a periphery of a light
interior. Alternatively, the lights 62 may be suspended at various
positions inside the tank 22. Each light 62 may comprise an
artificial light source such as an LED, or a natural light source
such as a network of fiber optic wave guides coupled to a solar
collector. The lights 62 are spaced throughout the tank primary
tank 22 to increase the volume inside the tank that receives
sufficient light to promote algae growth. The light apparatus 60
may additionally or alternatively include a light 64 positioned in
the circulation pipe 42 which creates a light zone in the pipe 42
through which the algae slurry passes as it flows through the pipe
42.
[0038] In operation, the inlet valve 31 is opened to permit algae
feed stock to be loaded into the primary tank 22 through the tank
inlet pipe 30. The inlet and outlet valves 31, 33 are then closed
to retain the algae feed stock in the primary tank 22. The light
apparatus 60 and sparger 50 are operated to provide the desired
amount of light and carbon dioxide in the tank 22 to create an
environment suitable for growing and cultivating a particular type
of algae. The algae feed stock is then agitated to increase the
amount of algae receiving sufficient light from the light apparatus
60. Agitation is accomplished primary by operating the circulation
system 40 and by the carbon dioxide bubbling through the liquid.
Agitation displaces the slurry so that different portions of the
algae are positioned adjacent the light apparatus 60, thereby
improving algae cultivation and minimizing or eliminating
putrefication of the algae. Additionally, the larger volume of
fluid that can be processed in the tank acts as a buffer to
maintain a more constant pH level.
[0039] An alternative embodiment of a bioreactor 120 is illustrated
in FIG. 2. The bioreactor 120 includes a primary tank 122 oriented
along a vertical axis 124. The vertical primary tank 122 may have
any commercially feasible size. For example, the tank 122 may have
a diameter of approximate twelve to twenty feet, and a height of
twenty to thirty feet, creating a corresponding volume of
approximately 17,000 to 70,000 gallons. The above dimensions and
volumes are merely exemplary, as the tank size may be scaled to the
desired algae output rate and/or available space. The primary tank
122 includes a first or bottom end 127 and a second or top end 128.
An inlet pipe 130 fluidly communicates with the interior of the
tank 122 near the end bottom 126, while an outlet pipe 132 fluidly
communicates with the interior of the tank 122 near the top end
128. Inlet and outlet valves 131, 133 are disposed in the inlet and
outlet pipes 130 and 132 respectively. A lid 136 is removably
coupled to the top end 128 of the primary tank 122 and is
configured to form an airtight seal when attached to the tank 122.
The primary tank 122 may be insulated, such as by fluid-filled
tubing 123 as illustrated in FIG. 11B.
[0040] The exemplary bioreactor 120 includes a gas delivery system
for introducing carbon dioxide into the primary tank 122. In the
illustrated embodiment, a sparger 150 is disposed near the bottom
end 126 of the primary tank 122 and includes a plurality of nozzles
152 for introducing carbon dioxide into the tank. The sparger 150
fluidly communicates with a gas inlet pipe 154 that is connected to
a source of carbon dioxide (not shown). A gas recirculating pipe
156 has an inlet in fluid communication with the top end 128 of the
primary tank 122 and an outlet in fluid communication with gas
inlet pipe 154. A pump 158 is disposed in the gas recirculating
pipe 156 to pull gas from the tank top end 128 and push gas to
through the sparger 150.
[0041] The bioreactor 120 further includes a mixer 170 for
agitating the algae feed stock inside the primary tank 122. As
illustrated in FIG. 2, the mixer 170 includes a rotatable shaft 172
disposed inside the primary tank 122. A plurality of turbine blades
174 is coupled to the shaft 172. The shaft 172 is operatively
coupled to a motor 176 which rotates the shaft 172 and attached
blade 174. In operation of the blades 174 displaces the algae
slurry inside the primary tank 122 so that the slurry is circulated
throughout the tank. The turbine blades 174 may include groups of
blades positioned at spaced elevations along the shaft 172 to form
discrete sets of turbine blades 178a, 178b, 178c. The shaft 172 may
further comprise segments that are supported for rotation in
different directions, thereby to provide counter-rotating turbine
blades. Other alternative blade configurations and styles are
disposed below that are suitable for use in the bioreactor 120.
[0042] The turbine blades 174 may be configured to maximize fluid
circulation inside the primary tank 122. As shown in FIG. 4a,
turbine blades 174a comprise radial blades that are substantially
linear. Each blade 174a is sized to extend from the shaft 172 to a
point near the interior surface of the primary tank 122. As shown
in FIG. 4b, the turbine blades 174b have a curved
configuration.
[0043] The turbine blades 174 may further includes means for
illuminating the algae slurry as well as for dispensing carbon
dioxide into the primary tank 122. An outer segment of turbine
blade 174 is schematically illustrated at FIG. 5. A light source,
such as an elongated light tube 180 is coupled to the turbine blade
174 and positioned near an exterior surface thereof. The turbine
blade 174 may include two or more light tubes 180 disposed on
opposed surfaces of the blade as shown in FIGS. 6a. Additionally, a
gas conduit 190 may extend longitudinally through the turbine blade
174. The gas conduit may include a primary conduit section 192
having an inlet in fluid communication with the central gas conduit
194 formed through the shaft 172. The primary segment 192 fluidly
communicates with a plurality of branches 196a-e which form outlets
198a-e (FIG. 6b) for discharging carbon dioxide into the primary
tank 122. Each turbine blade 174, or a sufficient number thereof,
used in the primary tank 122 may include a light tube 180 so that a
plurality of lights are disposed throughout the tank. Additionally,
each turbine blade 174 may include a gas conduit 190 to introduce
carbon dioxide simultaneously throughout the tank.
[0044] FIGS. 7A and 7B illustrate alternative turbine blade
arrangements. In FIG. 7A, a turbine blade 210 includes two light
tubes 212a, 212b extending along opposite sides of an exterior
surface thereof. A gas conduit 214 extends through the turbine
blade 210 and fluidly communicates with a source of carbon dioxide
(not shown). Branches 216a-c extend outwardly from the gas conduit
214 to form gas outlets 218a-c. At least some of the outlets, such
as outlets 218a and 218b, are positioned and oriented to discharge
carbon dioxide toward the light tubes 212a, 212b. For example,
outlet 218a is located near the light tube 212a. The branch 216a
leading to outlet 218a is angled toward the light tube 212a so that
gas exiting the outlet 218a initially flows toward the light tube
212a. The gas flow helps clear algae material from the turbine
blade 210 in the vicinity of the light tube 212a, thereby
increasing the effective area it illuminates inside the primary
tank.
[0045] FIG. 7B illustrates a simplified turbine blade 220 that
omits the carbon dioxide gas conduit. Instead, the turbine blade
220 includes an elongate light source 222 positioned at a leading
edge 224 of the blade 220.
[0046] The turbine blades may include separate sections which
permit complex fluid flow patterns to be formed inside the primary
tank 122. In the embodiment illustrated in FIGS. 8A and 8B, a
turbine blade 274 includes a primary section 276 positioned near a
shaft 272 and an outer section 278. At least one of the primary and
outer sections is oriented differently with respect to a remainder
of the blade 274 to create different fluid flow velocities and/or
directions. As shown in FIG. 8A, the outer section 278 is rotated
upward with respect to the primary section 276 to generate upward
fluid flow near the surface of the primary tank 122. A schematic of
this complex fluid flow path is provided at FIG. 10A, which shows
an inner fluid path section 280a flowing downward and an outer
fluid path section 282b flowing upward. The downward flow direction
of the larger, inner fluid path section 280a is counter to the flow
of carbon dioxide from the sparger located at a bottom of the
primary tank 122, thereby increasing the degree to which the algae
slurry is agitated. Conversely, FIG. 8B shows the primary section
276 rotated upwardly with respect to the outer section 278 to
create resulting upward and downward fluid flows respectively. A
schematic of this fluid flow path is provided at FIG. 10B, which
shows an inner fluid path section 280b flowing upward and an outer
fluid path section 282b flowing downward.
[0047] The velocities of each fluid path section may be altered by
the relative sizes of the primary and outer sections of the
rotating blades. In the embodiments illustrated in FIGS. 8A and 8B,
the blade primary section is significantly larger than the blade
outer section. As a result, the outer fluid path section has a
relatively higher velocity than the inner fluid path section, which
may advantageously remove adhered algae matter along the inner
surface of the primary tank 122 as well as any light sources
located thereon.
[0048] FIGS. 9A and 9B illustrate turbine blades 374 having three
different sections. As shown in FIG. 9A, the turbine blade 374
includes an inner section 375, a primary section 376 and an outer
section 378. As shown in FIG. 9A, the inner and outer sections 375,
378 are rotated upwardly with respect to the primary section 376
which will result in upward flows near the center and interior
surface of the primary tank 122, while the primary section 376 will
generate a downward fluid flow. A schematic of this fluid flow path
is provided at FIG. 10C, which shows inner and outer fluid path
sections 284a, 286a flowing downward and an intermediate fluid path
section 288a flowing upward. Conversely, as shown in FIG. 9B, the
primary section 376 has been rotated upwardly with respect to the
inner and outer sections 375, 378 to generate the opposite fluid
flow directions. A schematic of the resulting fluid flow path is
provided at FIG. 10D, which shows inner and outer fluid path
sections 284b, 286b flowing upward and an intermediate fluid path
section 288b flowing downward.
[0049] An alternative embodiment having both rotating and
non-rotating blades is illustrated in FIGS. 12A, 12B, and 13. As
best shown in FIG. 12A, the primary tank 122 includes a mixer 400
that includes a shaft 402 coupled to a motor 401. FIG. 12A
illustrates three alternative positions for the motor: (1) position
A near a top of and radially offset from the shaft 402; (2)
position B near a bottom of and radially offset from the shaft 402;
and (3) position C near a bottom of and axially aligned with the
shaft 402. The shaft 402 is further coupled to a plurality of
rotating blades 404. Additionally, non-rotating blades 406 extend
inwardly from the interior surface of the tank 122. The rotating
blades 404 define a rotating blade path that at least partially
overlaps the non-rotating blades 406 in an axial direction. Stated
another way, the rotating and non-rotating blades 404, 406 may be
axially aligned so that an axial fluid flow stream may encounter
both the rotating and non-rotating blades 404, 406 during
operation. Additionally, the non-rotating blades 406 may be
configured so that they permit removal of the rotating blades 404
from the primary tank 122, as shown in FIG. 12B, thereby
facilitating cleaning, repair, or replacement of the rotating
blades.
[0050] Both the rotating and non-rotating blades 404, 406 may be
configured to induce a desired fluid flow pattern inside the tank
122. As shown in FIG. 13, both sets of blades 404, 406 have an air
foil configuration. Each non-rotating blades 406 may incorporate
one or more light sources 408, as well as a carbon dioxide conduit
410, thereby simplifying these systems by eliminating the need to
route them through a rotating shaft. The carbon dioxide conduit 410
fluidly communicates with outlet orifices 412 positioned near the
light sources 408, so that gas flow exiting the outlet orifices 412
will clear algae material from the surfaces of the light sources
408. Additionally or alternatively, each rotating blades 404 may
include a carbon dioxide conduit 410a.
[0051] The rotating blades 404 may have inner and outer sections
404a, 404b to direct fluid flow in opposite directions as the blade
404 rotates. As shown in FIG. 14, the inner section 404a is
configured to generate an upward fluid flow adjacent the shaft 402,
while the outer section 404b is configured to generate a downward
fluid flow. The non-rotating blades 406 may also be configured as
shown to generate the downward fluid flow.
[0052] FIG. 15 shows an alternative embodiment similar to that
shown in FIG. 14. In FIG. 15, a rotating blade 420 has an inner
section 420a configured to create a downward fluid flow and an
outer section 420b configured to create an upward fluid flow. A
fixed blade 422 includes an outer post section 424 that is axially
aligned with the rotating blade outer section 420b and has a
profile that creates little resistance to the upward fluid flow
generated by the rotating blade outer section 420b. The fixed blade
422 also has an inner section 426 that is axially aligned with the
rotating blade inner section 420a and is configured to assist with
generating a downward fluid flow in the corresponding portion of
the tank.
[0053] FIG. 16 is a further alternative embodiment similar to that
of FIG. 15. The embodiment of FIG. 16 uses the same rotating blade
420 as in FIG. 15. A fixed blade 430, however, includes an outer
section 430b that is axially aligned with the rotating blade outer
section 420b and is configured to assist with generating an upward
fluid flow. The profile of the non-rotating blade outer section
430b also reduces the whirlpool effect generated by the rotating
blades 420. An inner section 430a of the fixed blade is axially
aligned with the rotating blade inner section 420a and is
configured to assist with generating a downward fluid flow in a
corresponding portion of the tank.
[0054] An alternative lighting source is illustrated in FIG. 17, in
which curved lighting panels 450 line an interior surface of the
primary tank 122. The curved lighting panels 450 may be formed
using flexible light panels that substantially conform to the shape
of the tank as they are applied to the tank interior surface, or
may be rigidly formed with substantially the same radius as the
tank and then attached to the tank interior surface. The lighting
panels 450 allow the entire interior surface of the tank side wall
to be used as a light source, thereby increasing the amount of
light generated inside the tank 122.
[0055] The bioreactors disclosed herein may be incorporated into a
production system 500 which provides the input materials to the
bioreactor and processes the algae cultivated in the bioreactor
into useful products. While FIG. 3 illustrates the system 500 that
uses the bioreactor 120, it will be appreciated that other
bioreactors including the bioreactor 20 disclosed herein may be
used without departing from the scope of the disclosure.
[0056] The water used in the bioreactor 120 may be taken from
various sources. Suitable water sources include fresh and/or
recycled water from a fish tank 502, sanitary sewer water 504, and
storm water detention and runoff 506. Any and all of these sources
may fluidly communicate with the inlet pipe 130 entering into the
bioreactor 120.
[0057] When using the fish tank 502 as the water source, the fish
tank 502 may fluidly communicate with a greenhouse 503 for
vegetable or plant production. Fish in the fish tank 502 fertilize
the algae used as feedstock in the bioreactor. Runoff from the
greenhouse 503 may include nutrients for the algae that are
detrimental to the fish, such as nitrogen. Nitrogen may be supplied
to the bioreactor with the algae feedstock and is subsequently
consumed during cultivation. As a result, a symbiotic system may be
provided where the bioreactor removes nitrogen from the water in
the fish tank while the fish fertilize the algae feedstock.
[0058] Any existing source of carbon dioxide may be coupled to the
gas inlet pipe 154. For example, the carbon dioxide source may be a
waste by-product from a separate process (list some possible
sources of carbon dioxide). Carbon dioxide may also be recirculated
from the tank top end 128 to the tank bottom end 126 through the
gas recirculation pipe 156.
[0059] Fully cultivated algae may be pumped through the tank outlet
pipe 122 to a separation tank 510. The separation tank 510
separates the algae into a lipid component and a polysaccarides
protein component, wherein each component is pumped to an
associated tank 512, 514. The lipids are piped to a
transesterfication unit 512 which uses an ultrasonic process to
create biodiesel which is pumped through outlet 516 and glycerin
which is pumped through outlet 518. The polysaccharides protein is
piped to a hydraulics unit 514 which uses an ultrasonic process to
produce proteins which exit through outlet 520 and mono sugars
which exit through outlet 522. The mono sugars may be piped to a
holding tank 524 where they are fermented into ethanol or other
alcohol compound. The ethanol from the fermenting tank 524 may be
further piped to a tanker vehicle 526 or to an additional tank 528
for further rapid fermentation processing. Throughout the process,
residual water and/or algae components may be returned to the
bioreactor 120 through a return pipe 530.
[0060] While only certain embodiments have been set forth,
alternatives and modifications will be apparent from the above
description to those skilled in the art. These and other
alternatives are considered equivalents and within the scope of
this disclosure and the appended claims.
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